The present invention relates to the inexpensive, compact, on-site storage of natural gas by an end user, utility, or gas supply or distribution company. More specifically, the present invention relates to the storage of natural gas by means of a facility comprising a steel pipe storage system configured and constructed as described herein which stores the gas in a compressed state. The facility of the present invention further comprises compressor and decompressor systems to compress natural gas upon injection from the utility, distribution or other supply transmission line into the steel pipe storage system and to decompress the gas upon withdrawal from the steel pipe storage system for injection into the user's facility or into a distribution pipeline for distribution and sale to others. The facility of the present invention further comprises means for containing the gas within the pipe storage system and controlling the flow of the gas to and from the facility.
Although not required elements of the present invention, optional filtering and/or drying systems may be incorporated into the facility to remove water and contaminants from the natural gas before it is stored in the steel pipe storage system. Further, the facility of the present invention may optionally include a multitude of controlling, monitoring and correcting systems, including monitoring systems measuring the humidity or water level ofthe gas prior to injection into the pipe storage system and cathodic protection systems lessening corrosion on, and test stations measuring the level of corrosion to, the steel pipes ofthe pipe storage system, all as described herein.
The present invention can be adapted for residential, commercial, industrial and utility applications, and enables end users to buy natural gas at lower prices, allows end users to have the same backup fuel supply as their primary supply, and enables utility companies and other suppliers/distributors of natural gas to store gas in a compact and inexpensive facility.
Currently, natural gas is delivered from a utility company or other supplier to an end user by means of a local utility gas distribution line, through a meter and into the end user's consumption line for immediate use by the end user. This delivery occurs at relatively low pressures, typically 5 pounds per square inch ("psi"). In return for lower rates, certain consumers (typically industrial or large commercial users) elect to receive their natural gas supplies on an "interruptible" basis, meaning that their supply of natural gas may be shut off or interrupted by the utility company or other supplier for a variety of reasons (e.g., curtailments due to excessively cold weather and insufficient line capacity). The growing demand for natural gas and limited utility line capacity could increase the frequency of interruptions for many of these consumers.
Large consumers subject to interruption of their natural gas supply typically have an alternate or backup fuel supply, such as propane fuel or fuel oil, stored on their property for use during periods of interruption. The use of a different backup fuel supply from the primary supply may make an additional facility to generate heat preferable. For example, where fuel oil is used as a backup fuel, the end user may have a backup facility comprised of a fuel oil-fired boiler or furnace. Alternatively, if the end user using fuel oil as a backup fuel does not have an additional boiler/furnace to burn the fuel oil, the burner of the boiler/furnace will need to be changed to one compatible with the use of fuel oil when the end user switches to its backup fuel supply. While end users using propane as their backup fuel supply typically use the same boiler as that used for natural gas, they may find it necessary to change the orifice through which fuel is injected into the burner of the boiler/furnace before switching the type of fuel supplied to the boiler/furnace. In many cases, the orifice must be smaller when using propane as compared to natural gas because of the higher heating units generated by burning propane. In order to avoid having to change orifices, some large industrial end users using propane fuel as a backup fuel supply have an alternate boiler/furnace to run exclusively on propane. Due to the higher heating units generated by propane or fuel oil, users of those fuels as their backup fuel supply may also have to change settings on certain manufacturing equipment.
End users using propane or fuel oil as a backup fuel supply must have a separate facility connected to the boiler/furnace to mix the propane or fuel oil with air prior to injection into the boiler/furnace. This additional facility causes some expense to the end user for maintaining the added facility and in employee training in the operations of said facility.
Per heating unit (btu), propane and fuel oil tend to be expensive in comparison to natural gas. Additionally, while the storage of propane as a backup fuel supply is typically noncontaminating, a leak of fuel oil creates hazardous conditions subject to expensive clean-up under the rules and regulations of the U.S. Environmental Protection Agency and state environmental agencies. Due to its low density, a leak or release of natural gas is not inherently contaminating and has no lasting environmental impact. Like propane, natural gas is potentially combustible if it mixes with air near an ignition source; however, the likelihood of natural gas combustion in use of the present invention is insignificant, presuming that the facility is properly manufactured, installed, operated and maintained. Your inventor prefers that the facility of the present invention be manufactured in accordance with U.S. Department of transportation ("DOT") regulations governing transmission pipeline systems. Transmission pipeline systems manufactured in accordance with those regulations have a very high safety record and correspondingly low incidence of actual combustion.
Because gas distribution companies charge less for interruptible gas service than for "firm" or non-interruptible service, the availability of natural gas as a backup fuel supply for use during periods of interruption affords end users the opportunity to achieve substantial energy cost savings while reducing the costs associated with alternative fuel supplies; further, in light of the expensive cost of propane and fuel oil in comparison to natural gas, use of natural gas as the end user's backup fuel supply would be advantageous. Moreover, due to the fluctuation in natural gas prices, it would be beneficial for end users to purchase substantial quantities of natural gas when the price is low and to store the gas until needed during periods of interruption or desired during periods when the price of natural gas is high. Finally, storage of natural gas as a backup fuel supply allows end users subject to interruption to utilize the same fuel and facilities in their backup operations.
In residential applications, users of this invention maybe able to store an entire year's worth of natural gas for their personal consumption, allowing them to purchase gas when rates are lowest.
Utility and other gas supply companies currently store natural gas in a compressed state by means of abandoned salt caverns, abandoned gas wells or other underground natural reservoirs. This storage and the processes and apparatuses associated therewith are described in U.S. Pat. No. 4,858,640. When the demand for natural gas exceeds current supply, utility companies inject a mixture of propane and air into the natural gas delivered to end users to increase the amount of gas supplied to a useable level. However, the number of heating units generated from propane-air is greater than that of natural gas, which may cause certain appliances and systems to malfunction (e.g., as regards gas stoves, the pilot light is set for a certain level of heating units specific to natural gas; excess heating units may cause the flame of the pilot light to burn higher, increasing the risk of fire). The propane-air stations used by utility companies to mix propane and air (accomplished through compressors designed for this purpose) and to inject the mixture with natural gas into transmission lines are regulated by state and federal environmental and other regulatory agencies, causing the cost of these facilities to be relatively expensive to maintain and requiring specialized professionals to operate the facilities.
Utility companies can benefit from the storage facility ofthe present invention, which allows them to compactly store additional natural gas which would complement or eliminate the need for propane storage and propane-air injection facilities. Further, utility companies can strategically locate facilities of the present invention near large users or heavily populated areas, eliminating the need to increase pipeline capacity. Unlike the preset locations of underground natural reservoirs, the facilities of the present invention may be strategically located anywhere there is suitable property to install the facility on.
Your inventor knows of no other methods to store natural gas other than in natural reservoirs, on ships for purposes of transporting natural gas and in small, tubular facilities used by suppliers of fuel for natural gas powered vehicles. The facilities for use by transporters of natural gas include those disclosed in the following U.S. Patents. U.S. Pat. No. 5,839,383 teaches the storage of compressed natural gas by means of continuous pipe wound in loops and layers and distributed within a container for purposes of transporting natural gas. U.S. Pat. No. 5,803,005 teaches the storage of compressed natural gas utilizing a plurality of gas cylinders for purposes of transporting natural gas by ship. The complicated systems in these patents not only cost more than the present invention, but are not suitable to efficiently store large quantities of natural gas on-site, available for use by an end user.
The facilities for use at vehicular fueling centers are described in the following U.S. Patents. U.S. Pat. No. 5,333,465 teaches the storage of compressed natural gas in underground tubes positioned vertically in an elongated casing. U.S. Pat. No. 5,207,530 teaches the underground storage of compressed natural gas by means of a plurality of underground storage containers. Again, the systems disclosed in these patents require many additional, and costly, components and are not suitable for on-site storage of large quantities of gas.
To be stored effectively in the storage facility ofthe present invention, it is necessary and desirable to compress the natural gas to a higher pressure (optimally 500 psi) than the standard pressure used in the end user's boiler (typically less than 10 psi). Further, regardless of pressure, the construction of the pipe storage system of the present invention should, and the preferred facilities disclosed herein is generally designed to, meet or exceed DOT Pipeline Safety Regulations, as they apply. Additional limitations may be prescribed by applicable state regulations (many states have adopted the federal standard to address safety issues on private end user pipeline systems).